Hob Sharpening problems cause & effect

Main Problem Areas seen in Sharpening

	Ø Run out the same as tool usage
	Ø Surface finish burning
	Ø Radiality
	Ø Gash Index

Run Out During Sharpening

Run out during Sharpening of Hobs is as important as in the use of Hobs. 

The same cause and effect is true.

See Hob run out errors

Some examples of Grinding Burns

When a Hob is "Burnt" like above the surface of the Hob is Softened behind the cutting surface this is called "White Layer" and can be seen below.

This type of "Burning" can cause "Crater wear" and in the extreme cause Hob failure

Alternatively Small micro cracks can be induced into the Hob and the failure as below is very common showing the "Half moon" tooth breakage which is a good sign of tooth breakage caused by Grinding crack's

Crack's can be seen on the left Photo

Radiality

Grinding tolerance 

For a 10 Dp 2.54 Mod Din 3968 

Class “A” 

Max 0.025mm (0.001”)